Change to Horizontal Separation Distance in Procedure F-6-1: Procedures to Govern Separation of Sewers and Watermains

This notice was originally posted in the old Environmental Registry under number 010-6816. 

Description of policy

The proposal is to revise the horizontal separation distance between watermains and sewers that is currently listed in Ministry Procedure F-6-1 from 2.5 metres to 3.0 metres in order to be consistent with industry best practices and protect public health.

Purpose of policy

Procedure F-6-1: Procedure to Govern Separation of Sewers and Watermains is a document that provides details on the ministry policy Guideline F-6: Sewer and Watermain Installation: Separation Distance Requirements. The current Procedure F-6-1 requires a horizontal separation distance between sewers and watermains of 2.5 metres, but revised Design Guidelines for Drinking-Water Systems and Sewage Works posted for consultation on March 20, 2008 contained a separation distance of 3.0 metres in order to be consistent with industry best practices and protect public health.

Because this separation distance is also covered in Procedure F-6-1, we are now proposing to update this Procedure. The rationale for an increase in the separation distances listed in Procedure F-6-1 from 2.5 metres to 3.0 metres is listed below:

• Distribution system contamination and bacterial growth on biofilms is influenced by transient water pressure fluctuation that creates pressure waves that travel through the pipes. During the negative cycle of the pressure wave, a substantial amount of contaminated water can be sucked in from outside the pipe, through a small leak. This problem is augmented when sewers are placed too close to watermains. Waterborne disease outbreaks have been linked to such systems. Aging infrastructure resulting in increased occurrence of leaks and main breaks will further compound the contamination.

• The Recommended Standards for Water Works (“Ten State Standards”) issued by the Great Lakes - Upper Mississippi River Board of State and Provincial Public Health and Environmental Managers, of which Ontario is a member, state that for a parallel installation water mains shall be laid at least 10 feet (approx. 3.0 metres) horizontally from any existing or proposed gravity sewer, septic tank, or subsoil treatment system. The distance shall be measured edge to edge.

• The Procedure for Disinfection of Drinking Water in Ontario (as referenced by O. Reg. 170/03

• One of the objectives in updating the Ministry’s Design Guidelines for Drinking-Water Systems and Sewage Works was to consolidate the Ministry’s existing Design Guidelines with the more current Ten State Standards document in addition to incorporating new technologies.

Other information

Procedure F-6-1: Procedure to Govern Separation of Sewers and Watermains – proposal would change “2.5 metres” to “3.0 metres” in all locations throughout the document.

Other public consultation opportunities

On March 20, 2008, the ministry consulted for 90 days on revised Design Guidelines for Drinking-Water Systems and Sewage Works where the draft versions indicated a horizontal separation distance between sewers and watermains of 3.0 metres, to be consistent with industry best practices and protect public health. Stakeholders and reviewers, including municipalities, engineers, environmental and legal associations, and operating agencies, were in favour of the 3.0 metre separation distance. Because this separation distance is also covered in Procedure F-6-1, we are now proposing to update this Procedure F-6-1. The final Design Guidelines were posted as decisions on December 19, 2008.